1. Field of The Invention
This invention relates to floating apparatus used in well casings, and more particularly, to a floating apparatus having an automatic filling body for allowing upward flow therethrough as the casing is lowered into a well.
2. Description of The Prior Art
An automatic fill-up floating apparatus is shown in Halliburton Services Sales and Service Catalog No. 43, pages 2431-2434. This apparatus may be used in either Halliburton Super Seal float collars of Halliburton Super Seal float shoes. An orifice sleeve is shearably attached to a valve stem and holds a valve element in an open position off a seat as the casing is lowered into the well. Two fluid orifices meter the flow and allow the casing to fill from below. The orifices are always open, and the orifice sleeve may be released from the valve stem by pumping a sufficient flow rate of fluid downwardly through the casing. This downward fluid flow through the orifices will cause a shear pin holding the valve stem to the sleeve to be sheared so that the sleeve will move downwardly therefrom, and the valve thereafter will be free to return to a fully closed position when the flow stops. In the float shoe configuration, the sleeve merely drops down the casing string below the entire apparatus. In the float collar configuration, a shoulder in the sleeve engages a shoulder on the valve stem to keep the orifice sleeve from falling on down the casing string while still allowing substantially full flow thereby for normal operation of the floating apparatus.
A problem with such previous automatic fill-up floating apparatus is that the orifices restrict flow as the casing is lowered into the well, and thus the differential pressure across the orifice sleeve is increased. This results in the casing string moving slowly down the well bore. Further, because downward flow through the orifices is not totally precise, the exact force applied to the sleeve is unknown, and the exact time at which shearing of the shear pin occurs is also not known. Positioning of the orifice sleeve must be very precise in this apparatus so that the orifices are in the proper relationship to the housing. Improper positioning may adversely affect the flow rate which could result in undesired release of the orifice sleeve or possibly failure of release. Also, the constant bypassing of fluid downwardly flowing through apparatus tends to clog up the orifices which again can result in improper actuation.
The automatic fill-up floating apparatus of the present invention solves these problems by providing a filling body pinned to the valve stem rather than an orifice sleeve. The filling body has a flow passage therethrough which is totally closed by a resilient washer in response to downward fluid movement through the apparatus. Precise alignment of the filling body is not required. The filling body will be moved, and thus the shear pin sheared, only when there is a known pressure differential across the washer. Thus, there is more precise tripping of the mechanism in the present invention than in the prior art.